EP3312653A1 - Endoscope objective optical system - Google Patents

Endoscope objective optical system Download PDF

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Publication number
EP3312653A1
EP3312653A1 EP16811476.7A EP16811476A EP3312653A1 EP 3312653 A1 EP3312653 A1 EP 3312653A1 EP 16811476 A EP16811476 A EP 16811476A EP 3312653 A1 EP3312653 A1 EP 3312653A1
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EP
European Patent Office
Prior art keywords
lens
optical system
objective optical
refractive power
endoscope
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP16811476.7A
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German (de)
English (en)
French (fr)
Inventor
Yasuaki Ushio
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Olympus Corp
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Olympus Corp
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Publication of EP3312653A1 publication Critical patent/EP3312653A1/en
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
    • G02B23/24—Instruments or systems for viewing the inside of hollow bodies, e.g. fibrescopes
    • G02B23/2407—Optical details
    • G02B23/2423—Optical details of the distal end
    • G02B23/243—Objectives for endoscopes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
    • A61B1/00064—Constructional details of the endoscope body
    • A61B1/00071—Insertion part of the endoscope body
    • A61B1/0008—Insertion part of the endoscope body characterised by distal tip features
    • A61B1/00096—Optical elements
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
    • A61B1/00163—Optical arrangements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
    • G02B9/34—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having four components only
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
    • G02B9/34—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having four components only
    • G02B9/58—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having four components only arranged - + + -

Definitions

  • the present invention relates to an objective optical system for endoscope which is small-sized and is to be used in an endoscope with a bright and highly-defined image quality.
  • the first problem is a problem caused due to an F-number.
  • a size of an aperture stop is also reduced to be scaled down. Consequently, there is a degradation of optical performance due to a diffraction of the small aperture stop. Therefore, if a design in which the F-number of the optical system is made fast is not made, a favorable optical performance cannot be achieved.
  • an aberration correction becomes difficult, and it is necessary to increase the number of lenses due to which the optical system tends to be large-sized.
  • the second problem is a problem of variation at the time of manufacturing.
  • For securing the optical performance when the size of the optical system is simply scaled down, it is necessary to scale down the manufacturing variation of the optical system in the same manner.
  • a method of making a refractive power of each lens weak is available.
  • the refractive power is made weak, the optical system becomes large-sized. Consequently, when an application in an objective optical system for endoscope is envisaged, a condition for small-sizing, which is essential for the objective optical system of endoscope, cannot be satisfied.
  • Patent Literature 1 The objective optical system for endoscope proposed in Patent Literature 1 is small-sized and arranged to have a fast F-number. However, an aberration correction performance is not adequate and cannot be applied as it is, for a large number of pixels.
  • the present invention has been made in view of the abovementioned circumstances, and an object of the present invention is to provide a small-sized and bright objective optical system for endoscope with a wide angle of view and thin diameter, which enables to achieve a highly-defined image.
  • the present invention provides the following means.
  • An objective optical system for endoscope includes in order from an object side, a front lens group having a negative refractive power as a whole, an aperture stop, and a rear lens group having a positive refractive power as a whole, wherein the front lens group includes in order from the object side, a first lens which is a single lens having a negative refractive power and a second lens which is a single lens having a positive refractive power, and the rear lens group includes a third lens which is a single lens having a positive refractive power and a cemented lens of a fourth lens having a positive refractive power and a fifth lens having a negative refractive power, and an object-side surface of the first lens is a flat surface, and the second lens has a meniscus shape having a convex surface directed toward an image side, and the third lens has a biconvex shape, and the objective optical system for endoscope satisfies the following conditional expression (1).
  • an effect is shown that it is possible to provide a small-sized and bright objective optical system for endoscope having a small number of lenses and a wide angle of view to deal with further thinning of a diameter and larger number of pixels of an endoscope.
  • Fig. 1 is a cross-sectional view of the arrangement of the objective optical system for endoscope according to the present embodiment.
  • the objective optical system for endoscope includes in order from an object side, a front lens group G1 having a negative refractive power as a whole, an aperture stop S, and a rear lens group G2 having a positive refractive power as a whole, wherein the front lens group G1 includes in order from the object side, a first lens L1 which is a single lens having a negative refractive power and a second lens L2 which is a single lens having a positive refractive power, and the rear lens group G2 includes a third lens L3 which is a single lens having a positive refractive power and a cemented lens L45 of a fourth lens L4 having a positive refractive power and a fifth lens L5 having a negative refractive power, and an object-side surface of the first lens L1 is a flat surface, and the second lens L2 has a meniscus shape having a convex surface directed toward an image side, and the third lens L3 has a biconvex shape, and the objective optical
  • the first lens L1 having a negative refractive power is disposed nearest to object. Accordingly, it is made possible to adopt a retro-focus type arrangement as the arrangement of the objective optical system.
  • the first lens L1 When a dirt or blood is adhered to a lens surface on the object side of the first lens L1 during the observation by endoscope, cleansing of the lens surface is carried out by jetting water from a nozzle provided at a front end of the endoscope. At the time of cleansing, when a shape of the lens surface of the object side of the first lens L1 is a convex shaped, the dirt is not removed easily. Moreover, when the shape of the lens surface on the object side of the first lens L1 is a concave shape, the water removal becomes unfavorable due to accumulation of water. Furthermore, when the lens surface of the object side of the first lens L1 is a convex surface, it is susceptible to be scratched or cracked due to an impact.
  • the first lens L1 having a negative refractive power is let to be a lens having planoconcave shape, the first lens L1 having a negative refractive power is disposed such that a flat surface is directed toward the object side.
  • the second lens L2 having a positive refractive power and a meniscus shape is disposed such that the convex surface is directed toward the image side.
  • the aperture stop S and a lens group having a positive refractive power of the third lens L3 having a positive refractive power and having a biconvex shape and the fourth lens L4 having a positive refractive power and having a biconvex shape are disposed on the image side of the second lens L2 having a meniscus shape.
  • the third lens L3 and the fourth lens L4 contribute mainly to image formation. Furthermore, dividing the positive refractive power between the third lens L3 having a positive refractive power and biconvex shape and the fourth lens L4 having a positive refractive power and biconvex shape, even when an F-number is made fast, it is possible to suppress the occurrence of aberration and to distribute the refractive power necessary for small-sizing.
  • the cemented lens L45 of the fourth lens L4 having a positive refractive power and biconvex shape and the fifth lens L5 having a negative refractive power is disposed at a position at which a height of a marginal ray on the image side of the third lens L3 becomes high.
  • a chromatic aberration is corrected by the cemented lens L45.
  • the first lens L1 having a negative refractive power is required to have a comparatively strong negative refractive power.
  • the negative refractive power of the first lens L1 is made excessively strong, an amount of aberration that occurs becomes excessively large. For instance, mainly a coma aberration and a chromatic aberration of magnification are not corrected thoroughly at the second lens L2 having a positive refractive power, and a spherical aberration is not corrected thoroughly at the third lens L3 having a positive refractive power and the fourth lens L4 having a positive refractive power, and an optical performance is degraded.
  • the optical system has a fast F-number, and it is possible to achieve both of the favorable optical performance and small-sizing.
  • conditional expression (1) When an upper limit value of conditional expression (1) is exceeded, the negative refractive power becomes excessively strong. Accordingly, the spherical aberration, the coma aberration, and the chromatic aberration occur and the performance is degraded, and an image quality is susceptible to be degraded due to the manufacturing variation.
  • conditional expression (1) When a value falls below a lower limit value of conditional expression (1), the negative refractive power becomes excessively weak. Accordingly, the overall length and a lens diameter of the objective optical system for endoscope become large, and the small-sizing cannot be carried out.
  • conditional expression (1') It is more desirable to satisfy the following conditional expression (1') instead of conditional expression (1). ⁇ 1.8 ⁇ f 1 / Ih ⁇ ⁇ 1.39
  • conditional expression (1") instead of conditional expression (1).
  • conditional expression (2) When an upper limit value of conditional expression (2) is exceeded, the radius of curvature of the object side of the third lens L3 becomes excessively large, and particularly the spherical aberration cannot be corrected, thereby leading to degradation of the optical performance.
  • conditional expression (2) 0.2 ⁇ SF 3 ⁇ 0.61
  • conditional expression (2) 0.3 ⁇ SF 3 ⁇ 0.5
  • conditional expression (3) When an upper limit value of conditional expression (3) is exceeded, a marginal performance is degraded due to the coma aberration in particular.
  • conditional expression (3) When a value falls below a lower limit value of conditional expression (3), the spherical aberration is degraded, and an aberration of the overall image field is degraded.
  • conditional expression (3) It is more desirable to satisfy the following conditional expression (3') instead of conditional expression (3). ⁇ 0.2 ⁇ SF 34 ⁇ 0.25
  • conditional expression (3) ⁇ 0.17 ⁇ SF 34 ⁇ 0.15
  • the first lens L1 having a negative refractive power and the fifth lens L5 having a negative refractive power satisfy the following conditional expression (4) in order to keep balance of the overall optical length and correction of the astigmatism in particular, in the periphery of image field. 0.15 ⁇ 1 / Fno ⁇ f 1 / f 5 ⁇ 0.3 where,
  • conditional expression (4) When an upper limit value of conditional expression (4) is exceeded, the refractive power of the first lens L1 becomes excessively weak, and either small-sizing becomes difficult or the refractive power of the fifth lens L5 becomes excessively strong and the astigmatism is corrected excessively, thereby leading to degradation of performance.
  • conditional expression (4) When a value falls below a lower limit value of conditional expression (4), either the refractive power of the first lens L1 becomes excessively strong or the refractive power of the fifth lens L5 becomes excessively weak, and the astigmatism cannot be corrected favorably, thereby making it difficult to achieve a favorable image quality. Moreover, it becomes an objective optical system having a slow F-number.
  • conditional expression (4') 0.17 ⁇ 1 / Fno ⁇ f 1 / f 5 ⁇ 0.27
  • conditional expression (4") 0.2 ⁇ 1 / Fno ⁇ f 1 / f 5 ⁇ 0.26
  • both the second lens L2 and the third lens L3 have a positive refractive power.
  • the second lens L2 and the third lens L3 are disposed to sandwich the aperture stop S in between. Therefore, it is an arrangement to cancel an aberration in the periphery of image field. However, with this arrangement, an aberration is not corrected adequately. Therefore, an arrangement of the fifth lens L5 having a negative refractive power at a position at which the height of the marginal light ray becomes high becomes significant.
  • conditional expression (5) When an upper limit value of conditional expression (5) is exceeded, either the refractive power of the second lens L2 and the refractive power of the third lens L3 become excessively strong and an aberration at a center and at the periphery of the image field is deteriorated, or the refractive power of the fifth lens L5 becomes excessively weak and an aberration at the periphery of the image field is not corrected adequately.
  • conditional expression (5) When a value falls below a lower limit value of conditional expression (5), either the refractive power of the second lens L2 and the refractive power of the third lens L3 become excessively weak and the overall length becomes large, or the refractive power of the fifth lens L5 becomes excessively strong and the chromatic aberration of magnification, the astigmatism, and an aberration at the periphery of the image field are corrected excessively.
  • conditional expression (5) ⁇ 1.5 ⁇ f 23 / f 5 ⁇ ⁇ 1.15
  • conditional expression (5) ⁇ 1.4 ⁇ f 23 / f 5 ⁇ ⁇ 1.1
  • the first lens L1 having a negative refractive power and the fourth lens L4 having a positive refractive power have an arrangement that bears a main function of retro-focus. Therefore, the first lens L1 having a negative refractive power and the fourth lens L4 having a positive refractive power are related to the overall optical length. Furthermore, the first lens L1 having a negative refractive power and the fourth lens L4 having a positive refractive power being away from the aperture stop S, are also related to the optical performance in the periphery of the image field. Therefore in the objective optical system for endoscope according to the present embodiment, it is desirable to satisfy the following conditional expression (6). ⁇ 1.1 ⁇ f 1 / f 4 ⁇ 0.7 where,
  • conditional expression (6) When an upper limit value of conditional expression (6) is exceeded, either the refractive power of the first lens L1 becomes weak and the overall length becomes large, or the refractive power of the fourth lens L4 becomes excessively strong and correction of the coma aberration becomes difficult.
  • conditional expression (6') ⁇ 1.0 ⁇ f 1 / f 4 ⁇ ⁇ 0.7
  • conditional expression (6) ⁇ 0.8 ⁇ f 1 / f 4 ⁇ ⁇ 0.7
  • Both the first lens L1 and the fourth lens L4 have a comparatively strong refractive power. Consequently, the first lens L1 and the fourth lens L4 have an effect on a curvature of field. Therefore, in the objective optical system for endoscope according to the present embodiment, it is desirable to satisfy the following conditional expression (7). 0.25 ⁇ R 1 R / R 4 L ⁇ 0.7 where,
  • conditional expression (7) When an upper limit value of conditional expression (7) is exceeded, the refractive power of the first lens L1 becomes excessively strong, and the image quality is susceptible to be degraded due to the manufacturing variation.
  • conditional expression (7') 0.25 ⁇ R 1 R / R 4 L ⁇ 0.45
  • conditional expression (7) instead of conditional expression (7).
  • the first lens L1 and the fifth lens L5 are disposed far away from the aperture stop S. Consequently, since the optical performance in the periphery of the image field is affected and the height of the marginal light ray becomes high, the lens diameter is also affected. Therefore, in the objective optical system for endoscope according to the present embodiment, it is desirable to satisfy the following conditional expression (8). ⁇ 0.3 ⁇ R 1 R / R 5 R ⁇ 0 where,
  • conditional expression (8) When an upper limit value of conditional expression (8) is exceeded, an angle of incidence of a light ray on an image pickup element becomes large, an attenuation of light occurs in a peripheral portion, and the back focus becomes short leading to a deterioration of assemblability.
  • conditional expression (8') It is more desirable to satisfy the following conditional expression (8') instead of conditional expression (8). ⁇ 0.21 ⁇ R 1 R / R 5 R ⁇ 0
  • conditional expression (8) ⁇ 0.1351 ⁇ R 1 R / R 5 R ⁇ 0
  • conditional expression (9') It is more desirable to satisfy the following conditional expression (9') instead of conditional expression (9). ⁇ ⁇ 65°
  • Fig. 2A is a cross-sectional view of the objective optical system for endoscope according to the present example
  • Fig. 2B shows a spherical aberration (SA)
  • Fig. 2C shows an astigmatism (AS)
  • Fig. 2D shows a distortion (DT)
  • Fig. 2E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • SA spherical aberration
  • AS astigmatism
  • Fig. 2D shows a distortion
  • Fig. 2E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • CC chromatic aberration of magnification
  • the objective optical system for endoscope includes in order from an object side, a first lens L1 having a negative refractive power and having a planoconcave shape with a flat surface directed toward the object side, a second meniscus lens L2 having a positive refractive power and having a convex surface directed toward an image side, an infra-red absorbing filter F1, an aperture stop S, a third lens L3 having a positive refractive power and having a biconvex shape, a fourth lens L4 having a positive refractive power and having a biconvex shape, a fifth meniscus lens L5 having a negative refractive power and having a convex surface directed toward the image side, a cover glass CG1, and an image pickup element cover glass CG2.
  • the fourth lens L4 having a positive refractive power and the fifth meniscus lens L5 having a negative refractive power are cemented.
  • the cover glass CG1 and the image pickup element cover glass CG2 are cemented via a cemented layer F2.
  • IMG denotes an image pickup surface.
  • Fig. 3A is a cross-sectional view of the objective optical system for endoscope according to the present example
  • Fig. 3B shows a spherical aberration (SA)
  • Fig. 3C shows an astigmatism (AS)
  • Fig. 3D shows a distortion (DT)
  • Fig. 3E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • the objective optical system for endoscope includes in order from an object side, a first lens L1 having a negative refractive power and having a planoconcave shape with a flat surface directed toward the object side, a second meniscus lens L2 having a positive refractive power and having a convex surface directed toward an image side, an infra-red absorbing filter F1, an aperture stop S, a third lens L3 having a positive refractive power and having a biconvex shape, a fourth lens L4 having a positive refractive power and having a biconvex shape, a fifth meniscus lens L5 having a negative refractive power and having a convex surface directed toward the image side, a cover glass CG1, and an image pickup element cover glass CG2.
  • the fourth lens L4 having a positive refractive power and the fifth meniscus lens L5 having a negative refractive power are cemented.
  • the cover glass CG1 and the image pickup element cover glass CG2 are cemented via a first lens
  • Fig. 4A is a cross-sectional view of the objective optical system for endoscope according to the present example
  • Fig. 4B shows a spherical aberration (SA)
  • Fig. 4C shows an astigmatism (AS)
  • Fig. 4D shows a distortion (DT)
  • Fig. 4E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • the objective optical system for endoscope includes in order from an object side, a first lens L1 having a negative refractive power and having a planoconcave shape with a flat surface directed toward the object side, a second meniscus lens L2 having a positive refractive power and having a convex surface directed toward an image side, an infra-red absorbing filter F1, an aperture stop S, a third lens L3 having a positive refractive power and having a biconvex shape, a fourth lens L4 having a positive refractive power and having a biconvex shape, a fifth meniscus lens L5 having a negative refractive power and having a planoconcave shape with a flat surface directed toward the image side, a cover glass L6 having a planoconvex shape with a convex surface directed toward the object side, and an image pickup element cover glass CG.
  • the fourth lens L4 having a positive refractive power and the fifth lens L5 having a negative refractive power
  • Fig. 5A is a cross-sectional view of the objective optical system for endoscope according to the present example
  • Fig. 5B shows a spherical aberration (SA)
  • Fig. 5C shows an astigmatism (AS)
  • Fig. 5D shows a distortion (DT)
  • Fig. 5E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • SA spherical aberration
  • AS astigmatism
  • Fig. 5D shows a distortion
  • Fig. 5E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • CC chromatic aberration of magnification
  • the objective optical system for endoscope includes in order from an object side, a first lens L1 having a negative refractive power and having a planoconcave shape with a flat surface directed toward the object side, a second meniscus lens L2 having a positive refractive power and having a convex surface directed toward an image side, an infra-red absorbing filter F1, an aperture stop S, a third lens L3 having a positive refractive power and having a biconvex shape, a fourth lens L4 having a positive refractive power and having a biconvex shape, a fifth meniscus lens L5 having a negative refractive power and having a convex surface directed toward the image side, a cover glass L6 having a planoconvex shape with a convex surface directed toward the object side, and an image pickup element cover glass CG.
  • the fourth lens L4 having a positive refractive power and the fifth meniscus lens L5 having a negative refractive power are cemented.
  • Fig. 6A is a cross-sectional view of the objective optical system for endoscope according to the present example
  • Fig. 6B shows a spherical aberration (SA)
  • Fig. 6C shows an astigmatism (AS)
  • Fig. 6D shows a distortion (DT)
  • Fig. 6E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • the objective optical system for endoscope includes in order from an object side, a first lens L1 having a negative refractive power and having a planoconcave shape with a flat surface directed toward the object side, a second meniscus lens L2 having a positive refractive power and having a convex surface directed toward an image side, an infra-red absorbing filter F1, an aperture stop S, a third lens L3 having a positive refractive power and having a biconvex shape, a fourth lens L4 having a positive refractive power and having a biconvex shape, a fifth meniscus lens L5 having a negative refractive power and having a convex surface directed toward the image side, a cover glass CG1, and an image pickup element cover glass CG2.
  • the fourth lens L4 having a positive refractive power and the fifth meniscus lens L5 having a negative refractive power are cemented.
  • the cover glass CG1 and the image pickup element cover glass CG2 are cemented via a first lens
  • Fig. 7A is a cross-sectional view of the objective optical system for endoscope according to the present example
  • Fig. 7B shows a spherical aberration (SA)
  • Fig. 7C shows an astigmatism (AS)
  • Fig. 7D shows a distortion (DT)
  • Fig. 7E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • the objective optical system for endoscope includes in order from an object side, a first lens L1 having a negative refractive power and having a planoconcave shape with a flat surface directed toward the object side, a second meniscus lens L2 having a positive refractive power and having a convex surface directed toward an image side, an infra-red absorbing filter F1, an aperture stop S, a third lens L3 having a positive refractive power and having a biconvex shape, a fourth lens L4 having a positive refractive power and having a biconvex shape, a fifth lens L5 having a negative refractive power and having a planoconcave shape with a flat surface directed toward the image side, a cover glass CG1, and an image pickup element cover glass CG2.
  • the fourth lens L4 having a positive refractive power and the fifth lens L5 having a negative refractive power are cemented.
  • the cover glass CG1 and the image pickup element cover glass CG2 are cemented.
  • Fig. 8A is a cross-sectional view of the objective optical system for endoscope according to the present example
  • Fig. 8B shows a spherical aberration (SA)
  • Fig. 8C shows an astigmatism (AS)
  • Fig. 8D shows a distortion (DT)
  • Fig. 8E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • SA spherical aberration
  • AS astigmatism
  • Fig. 8D shows a distortion
  • Fig. 8E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • CC chromatic aberration of magnification
  • the objective optical system for endoscope includes in order from an object side, a first lens L1 having a negative refractive power and having a planoconcave shape with a flat surface directed toward the object side, a second meniscus lens L2 having a positive refractive power and having a convex surface directed toward an image side, an infra-red absorbing filter F1, an aperture stop S, a third lens L3 having a positive refractive power and having a biconvex shape, a fourth lens L4 having a positive refractive power and having a biconvex shape, a fifth meniscus lens L5 having a negative refractive power and having a convex surface directed toward the image side, a cover glass CG1, and an image pickup element cover glass CG2.
  • the fourth lens L4 having a positive refractive power and the fifth meniscus lens L5 having a negative refractive power are cemented.
  • the cover glass CG1 and the image pickup element cover glass CG2 are cemented via a first lens
  • Fig. 9A is a cross-sectional view of the objective optical system for endoscope according to the present example
  • Fig.9B shows a spherical aberration (SA)
  • Fig. 9C shows an astigmatism (AS)
  • Fig. 9D shows a distortion (DT)
  • Fig. 9E shows a chromatic aberration of magnification (CC) for the objective optical system for endoscope according to the present example.
  • the objective optical system for endoscope includes in order from an object side, a first lens L1 having a negative refractive power and having a planoconcave shape with a flat surface directed toward the object side, a second meniscus lens L2 having a positive refractive power and having a convex surface directed toward an image side, an infra-red absorbing filter F1, an aperture stop S, a third lens L3 having a positive refractive power and having a biconvex shape, a fourth lens L4 having a positive refractive power and having a biconvex shape, a fifth meniscus lens L5 having a negative refractive power and having a convex surface directed toward the image side, a cover glass CG1, and an image pickup element cover glass CG2.
  • the fourth lens L4 having a positive refractive power and the fifth meniscus lens L5 having a negative refractive power are cemented.
  • the cover glass CG1 and the image pickup element cover glass CG2 are cemented via a first lens
  • r denotes a radius of curvature of each lens surface
  • d denotes a distance between two lens surfaces
  • ne denotes a refractive index for an e-line of each lens
  • ⁇ d denotes Abbe's number for each lens
  • Fno denotes an F-number
  • ⁇ denotes a half angle of view
  • IH denotes an image height.
  • the present invention is useful for a small-sized and bright objective optical system for endoscope having a wide angle of view, which achieves a highly-defined image.

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EP16811476.7A 2015-06-18 2016-06-03 Endoscope objective optical system Withdrawn EP3312653A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2015123031 2015-06-18
PCT/JP2016/066673 WO2016204001A1 (ja) 2015-06-18 2016-06-03 内視鏡用対物光学系

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US (1) US10018827B2 (zh)
EP (1) EP3312653A1 (zh)
JP (1) JP6109461B1 (zh)
CN (1) CN107003503B (zh)
WO (1) WO2016204001A1 (zh)

Cited By (2)

* Cited by examiner, † Cited by third party
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TWI709783B (zh) * 2019-12-19 2020-11-11 大陸商信泰光學（深圳）有限公司 廣角鏡頭（二十八）
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